This invention relates to diffusing lens panels for controlling the light output from gas discharge lamps of circular shape, such as the circline type fluorescent lamps in general use, to direct the widely dispersed light from the lamp into a directional beam of useful light, with reduced side glare and efficiency losses.
Circular fluorescent lamps have been widely used in lampholder fittings, such as those described in my inventions of U.S. Pat. Nos. 4,105,276 and 4,178,535, in which bare, exposed lamps are used as screw-in ceiling fixtures and as sources in portable lamps which use shades to direct and control the light. In my co-pending application entitled A CIRCULAR GAS DISCHARGE REFLECTOR LAMP, Ser. No. 409,999, now U.S. Pat. No. 4,420,799, optical control of the lamp is shown by both reflective and refractive means, a refractive means shown therein being the male prism pattern which faces away from the lamp.
The purpose of the present invention is to provide more precise and effective optical control than is possible with the use of a single optical surface, to essentially produce a spotlight or narrow beam floodlight from a fluorescent source of circular shape, and also to produce a lens for the circular fluorescent source that is adapted for use in fixtures and lampholder fittings which also include light control by means of reflectors.